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151 lines
6.4 KiB
Python
151 lines
6.4 KiB
Python
#!/usr/bin/env python3
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# Author: OMKAR PATHAK, Nwachukwu Chidiebere
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# Use a Python dictionary to construct the graph.
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from __future__ import annotations
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from pprint import pformat
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from typing import Generic, TypeVar
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T = TypeVar("T")
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class GraphAdjacencyList(Generic[T]):
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"""
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Adjacency List type Graph Data Structure that accounts for directed and undirected
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Graphs. Initialize graph object indicating whether it's directed or undirected.
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Directed graph example:
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>>> d_graph = GraphAdjacencyList()
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>>> print(d_graph)
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{}
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>>> d_graph.add_edge(0, 1)
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{0: [1], 1: []}
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>>> d_graph.add_edge(1, 2).add_edge(1, 4).add_edge(1, 5)
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{0: [1], 1: [2, 4, 5], 2: [], 4: [], 5: []}
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>>> d_graph.add_edge(2, 0).add_edge(2, 6).add_edge(2, 7)
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{0: [1], 1: [2, 4, 5], 2: [0, 6, 7], 4: [], 5: [], 6: [], 7: []}
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>>> d_graph
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{0: [1], 1: [2, 4, 5], 2: [0, 6, 7], 4: [], 5: [], 6: [], 7: []}
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>>> print(repr(d_graph))
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{0: [1], 1: [2, 4, 5], 2: [0, 6, 7], 4: [], 5: [], 6: [], 7: []}
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Undirected graph example:
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>>> u_graph = GraphAdjacencyList(directed=False)
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>>> u_graph.add_edge(0, 1)
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{0: [1], 1: [0]}
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>>> u_graph.add_edge(1, 2).add_edge(1, 4).add_edge(1, 5)
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{0: [1], 1: [0, 2, 4, 5], 2: [1], 4: [1], 5: [1]}
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>>> u_graph.add_edge(2, 0).add_edge(2, 6).add_edge(2, 7)
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{0: [1, 2], 1: [0, 2, 4, 5], 2: [1, 0, 6, 7], 4: [1], 5: [1], 6: [2], 7: [2]}
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>>> u_graph.add_edge(4, 5)
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{0: [1, 2],
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1: [0, 2, 4, 5],
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2: [1, 0, 6, 7],
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4: [1, 5],
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5: [1, 4],
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6: [2],
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7: [2]}
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>>> print(u_graph)
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{0: [1, 2],
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1: [0, 2, 4, 5],
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2: [1, 0, 6, 7],
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4: [1, 5],
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5: [1, 4],
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6: [2],
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7: [2]}
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>>> print(repr(u_graph))
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{0: [1, 2],
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1: [0, 2, 4, 5],
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2: [1, 0, 6, 7],
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4: [1, 5],
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5: [1, 4],
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6: [2],
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7: [2]}
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>>> char_graph = GraphAdjacencyList(directed=False)
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>>> char_graph.add_edge('a', 'b')
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{'a': ['b'], 'b': ['a']}
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>>> char_graph.add_edge('b', 'c').add_edge('b', 'e').add_edge('b', 'f')
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{'a': ['b'], 'b': ['a', 'c', 'e', 'f'], 'c': ['b'], 'e': ['b'], 'f': ['b']}
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>>> char_graph
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{'a': ['b'], 'b': ['a', 'c', 'e', 'f'], 'c': ['b'], 'e': ['b'], 'f': ['b']}
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"""
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def __init__(self, directed: bool = True) -> None:
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"""
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Parameters:
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directed: (bool) Indicates if graph is directed or undirected. Default is True.
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"""
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self.adj_list: dict[T, list[T]] = {} # dictionary of lists
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self.directed = directed
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def add_edge(
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self, source_vertex: T, destination_vertex: T
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) -> GraphAdjacencyList[T]:
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"""
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Connects vertices together. Creates and Edge from source vertex to destination
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vertex.
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Vertices will be created if not found in graph
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"""
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if not self.directed: # For undirected graphs
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# if both source vertex and destination vertex are both present in the
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# adjacency list, add destination vertex to source vertex list of adjacent
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# vertices and add source vertex to destination vertex list of adjacent
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# vertices.
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if source_vertex in self.adj_list and destination_vertex in self.adj_list:
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self.adj_list[source_vertex].append(destination_vertex)
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self.adj_list[destination_vertex].append(source_vertex)
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# if only source vertex is present in adjacency list, add destination vertex
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# to source vertex list of adjacent vertices, then create a new vertex with
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# destination vertex as key and assign a list containing the source vertex
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# as it's first adjacent vertex.
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elif source_vertex in self.adj_list:
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self.adj_list[source_vertex].append(destination_vertex)
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self.adj_list[destination_vertex] = [source_vertex]
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# if only destination vertex is present in adjacency list, add source vertex
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# to destination vertex list of adjacent vertices, then create a new vertex
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# with source vertex as key and assign a list containing the source vertex
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# as it's first adjacent vertex.
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elif destination_vertex in self.adj_list:
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self.adj_list[destination_vertex].append(source_vertex)
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self.adj_list[source_vertex] = [destination_vertex]
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# if both source vertex and destination vertex are not present in adjacency
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# list, create a new vertex with source vertex as key and assign a list
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# containing the destination vertex as it's first adjacent vertex also
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# create a new vertex with destination vertex as key and assign a list
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# containing the source vertex as it's first adjacent vertex.
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else:
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self.adj_list[source_vertex] = [destination_vertex]
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self.adj_list[destination_vertex] = [source_vertex]
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# For directed graphs
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# if both source vertex and destination vertex are present in adjacency
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# list, add destination vertex to source vertex list of adjacent vertices.
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elif source_vertex in self.adj_list and destination_vertex in self.adj_list:
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self.adj_list[source_vertex].append(destination_vertex)
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# if only source vertex is present in adjacency list, add destination
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# vertex to source vertex list of adjacent vertices and create a new vertex
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# with destination vertex as key, which has no adjacent vertex
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elif source_vertex in self.adj_list:
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self.adj_list[source_vertex].append(destination_vertex)
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self.adj_list[destination_vertex] = []
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# if only destination vertex is present in adjacency list, create a new
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# vertex with source vertex as key and assign a list containing destination
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# vertex as first adjacent vertex
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elif destination_vertex in self.adj_list:
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self.adj_list[source_vertex] = [destination_vertex]
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# if both source vertex and destination vertex are not present in adjacency
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# list, create a new vertex with source vertex as key and a list containing
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# destination vertex as it's first adjacent vertex. Then create a new vertex
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# with destination vertex as key, which has no adjacent vertex
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else:
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self.adj_list[source_vertex] = [destination_vertex]
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self.adj_list[destination_vertex] = []
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return self
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def __repr__(self) -> str:
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return pformat(self.adj_list)
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